Probes for Narcotic Receptor Mediated Phenomena. 17. Synthesis and Evaluation of a Series of trans-3,4-Dichloro-N-methyl-N-benzeneacetamide (U50,488) Related Isothiocyanate Derivatives as Opioid Receptors Affinity Ligands

Article abstract of DOI:10.1021/jm00166a014

A series of U50,488 related isothiocyanates was synthesized from enantiomerically pure (S,S)-(+)-trans-2-pyrrolidinyl-N-methylcyclohexylamine <(+)-7> and (R,R)-(-)-trans-2-pyrrolidinyl-N-methylcyclohexylamine <(-)-7>.DCC coupling of (+)- and (-)-7 with nitrophenylacetic acids followed by catalytic hydrogenation and treatment with thiophosgene afforded a series of six isomeric aryl isothiocyanate analogues of U50,488.Similarly, DCC coupling of (+)- and (-)-7 with (+)- and (-)-N-t-Boc-protected phenylglycines afforded four isomeric alkyl isothiocyanates.Evaluation ofthe isothiocyanates for their capacity to produce wash-resistant inhibition of μ, δ, and κ sites in vitro was performed using rat and guinea pig brain membranes.None of the compounds was able to irreversibly inhibit binding of <3H>bremazocine to guinea pig and rat brain membranes (depleted of functional μ and δ receptors by pretreatment with acylating agents BIT and FIT).However, (1S,2S)-trans-2-isothiocyanato-N-methyl-N-<2-(1-pyrrolidinyl)cyclohexyl>benzeneacetamide <(-)-1> was able to specifically and irreversibly inhibit κ receptors labeled by <3H>-U69,593: Incubation of rat brain membranes for 60 min at 25 deg C with 1 μM of (-)-1 resulted in a wash-resistant reduction of the binding to 11.2 +/- 2.5percent of the control.Binding analysis revealed the wash-resistant reduction in <3H>-U69,593 binding by (-)-1 to be through an increase in the K_dwithout effect on the B_max. (-)-1 failed to effect μ or δ binding in rat or guinea pig under the same conditions.The enatiomer of (-)-1, (1R,2R)-trans-2-isothiocyanato-N-methyl-N-<2-(1-pyrrolidinyl)cyclohexyl>benzeneacetamide <(+)-1>, failed to affect κ receptors labeled by<3H>-U69,593 under the same conditions as for (-)-1. (1S,2S)-trans-3-Isothiocyanato-N-methyl-N-<2-(1-pyrrolidinyl)cyclohexyl>benzeneacetamide <(-)-2> inhibited to 49.6 +/- 5.1percent of the control, in a wash-resistant manner, κ receptors labeled by <3H>-U69,593.However, (-)-2 was not as selective as (-)-1 since it also reduced <3H>DADLE (δ) binding to 82.4 +/-8.9percent of the control value. (1S,2S)-trans-4-Isothiocyanato-N-methyl-N-<2-(1-pyrrolidinyl)cyclohexyl>benzeneactamide <(-)-3>exhibited selective wash-resistant inhibition of δ receptors labeled by <3H>DADLE resulting in a reduction in binding to 42.9 +/- 4.2percent of control.In the alkyl isothiocyanate series, (1S,2S)-trans-N-methyl-N-<2-(1-pyrrolidinyl)cyclohexyl>-(S)-2-phenyl-2-isothiocyanatoaceatmide <(-)-11> also showed the capacity to selectively inhibit <3H>-U69,593-sensitive κ sites, resulting in a reduction in binding to 72,2 +/- 2.54percent of control at 1 μM while (+)-11 was inactive.None of the amino precursors (-)-8, (+)-8, (-)-9, (+)-9, (-)-10, (+)-10, (-)-15, (+)-15, (-)-16, and (+)-16 of the isothiocyanates exhibited the capacity for wash-resistant inhibition of any of the receptor systems tested. ...